The long-term objectives of this project are (1) to develop an understanding of the basic physiological mechanisms of lacrimal gland protein secretion and (2) to determine what age-related changes occur that diminish secretory activity and result in keratoconjunctivitis (KCS; dry eye) which is detrimental to the cornea. The increased knowledge of specific age-related changes in stimulus-response coupling will provide the basis for designing improved treatment to alleviate pain and deleterious effects on the cornea which are due to aging of the lacrimal gland. The following specific goals will accomplish the long-term objectives: (1) Establish tissue culture conditions for the growth and differentiation of lacrimal duct and acinar epithelial cells. (2) Validate the differentiated state of the culture duct and acinar epithelial cells by histochemical, cytological and physiological techniques. (3) Compare the in vitro growth and physiological responsiveness of lacrimal duct and acinar tissue from young rats (1-4 mos old) to that from aged rats (12-24 mos old). (4) Determine how long duct and acinar cells can be maintained in culture and compare the longevity of cells derived from young rats with those derived from aged rats. (5) Determine if the histological and physiological changes that occur in cells from young animals as they age in culture are similar to the changes seen in freshly isolated cells from aged animals. Lacrimal glands from F344 rats will be used to establish cultures of duct and acinar epithelia. Donors (both sexes) will be 1, 4, 12 and 24 months old, corresponding to human equivalents of juvenile, young adult, midage, and old age. The cultures, initiated with tissue explants or cells from dissociated glands, will be established on supported filters coated with an extracellular matrix. Intact gland and cell cultures will be examined by immunofluorescence and enzyme histochemistry for cytokeratins, secretory component, lacrimal peroxidase, carbonic anhydrase and gamma-glutamyl transferase to confirm the presence of differentiated duct and acinar cells. Cultured cells will be stimulated with autonomic agonists to secrete radio-labeled exocytotic proteins. Rates of secretion will be measured, and the electrophoretic pattern of secreted proteins will be determined by fluorography.